Evolution of a Viscous Protoplanetary Disk with Convectively Unstable Regions. II. Accretion Regimes and Long-Term Dynamics

TL;DR

This study models the long-term evolution of viscous protoplanetary disks, demonstrating that convection can cause episodic accretion and instability over millions of years, with implications for star formation processes.

Contribution

It provides a detailed analysis of how convective instability influences accretion regimes and disk evolution, extending previous models to include long-term dynamics and matter inflow variations.

Findings

Burst-like accretion occurs over a wide parameter range

Convective instability persists for several million years

Outer disk regions can become gravitationally unstable

Abstract

In this article, we proceed to study convection as a possible factor of episodic accretion in protoplanetary disks. Within the model presented in Article~I, the accretion history is analyzed at different rates and areas of matter inflow from the envelope onto the disk. It is shown that the burst-like regime occurs in a wide range of parameters. The long-term evolution of the disk is also modeled, including the decreasing-with-time matter inflow from the envelope. It is demonstrated that the disk becomes convectively unstable and maintains burst-like accretion onto the star for several million years. Meanwhile, the instability expands to an area of several tens of astronomical units and gradually decreases with time. It is also shown that at early stages in the disk evolution, conditions arise for gravitational instability in the outer parts of the disk and for dust evaporation in the convectively unstable inner regions. The general conclusion of the study is that convection can serve as one of the mechanisms of episodic accretion in protostellar disks, but this conclusion needs to be verified using more consistent hydrodynamic models.